Keywords common bile duct - compression - inferior pancreaticoduodenal artery - magnetic cholangiopancreatography
Introduction
Various benign and malignant pathologies/conditions can cause compression of the extrahepatic
biliary system (EBS). Anatomical and topographic variations, especially those of vessels',
are not infrequent in this region. Thus, anatomical and topographic variations should
be given special consideration as a probable cause of the EBS compression, specifically
in patients with no obvious etiology. Among these variations, the right hepatic artery
was the first to be recognized as a possible cause of the EBS compression.[1 ] Hence, the authors proposed to name the condition as “right hepatic artery compression
syndrome” in 1984.[1 ] Topographic variations in arterial anatomy neighboring EBS have been a matter of
concern since then.
There is only one publication, of which we are aware, that describes the posterosuperior
pancreaticoduodenal artery compressing the common bile duct (CBD).[2 ] To the best of our knowledge, this is the second case in the English literature
where tortuous and enlarged inferior pancreaticoduodenal artery (IPdA) branches were
suspected to result in impaired liver function tests.
Case Description
A 68-year-old man was referred to our abdominal imaging division for further diagnostic
workup of impaired liver function tests. The patient did not have any specific symptoms
on admission that could be attributed to the elevated liver function tests. He had
a past medical history of hypertension, coronary artery disease, type 2 diabetes mellitus,
and myasthenia gravis. His family history was unremarkable. Physical examination revealed
no abnormal findings. No jaundice was observed. No palpable mass was noted in the
right upper quadrant. Biochemical analyses of the liver functions on admission showed
mildly increased alanine aminotransferase of 75 IU/L (normal range: 0–50 U/L), aspartate
aminotransferase of 68 IU/L (normal range: 0–50 U/L), and gamma-glutamyl transferase
of 116 IU/L (normal range: 0–55 U/L). Total bilirubin was 0.68 mg/dL (normal range:
0.3–1.2 mg/dL), conjugated bilirubin was 0.17 mg/dL (normal range: 0–0.2 mg/dL), and
alkaline phosphatase was 99 IU/L (normal range: 30–120 U/L). The patient was tested
negative for hepatitis B surface antigen and antihepatitis C virus. Alpha-fetoprotein
level was within the normal range (0–9 ng/mL).
The hepatobiliary ultrasound (US) examination showed the increased echogenicity of
the periportal regions as well as an echogenic nodular mass in segment 7 (not shown).
Triphasic computed tomography (CT) of the liver was subsequently performed to specify
the incidentally detected lesion further. And the CT displayed a hypodense nodular
mass in segment 7 with a centripetal fill-in pattern on post-contrast consecutive
images, characteristic of a hemangioma (not shown). Triphasic CT of the liver also
revealed the arterial compression onto the distal CBD by tortuous and enlarged IPdA
branches with complicating atheromatous changes adding to the described pathology
([Figs. 1 ] and [Figs. 2 ]). Further examination of the CT images established the severe stenosis of the celiac
trunk orifice ([Fig. 3A, B ]). No benign nor malignant mass was noted in the periportal region. Meanwhile, magnetic
cholangiopancreatography (MRCP) was performed to clarify the cause of the elevated
liver enzymes, and showed the mild upstream dilation of the EBS, just cranial to the
arterial compression site on the distal CBD ([Fig. 4A, C ]). When the findings of the CT and MRCP scans evaluated together, it was speculated
that the distal CBD compression by tortuous and enlarged IPdA branches, namely anterior
and posterior, might have been the underlying cause of impaired liver function tests.
Fig. 1 Axial (A ) and coronal (B ) computed tomographic images showing the arterial compression onto the distal common
bile duct (arrows) by tortuous and enlarged inferior pancreaticoduodenal artery branches.
Fig. 2 Three-dimensional volume-rendered standard (A ) and zoomed-in (B ) computed tomographic images displaying the tortuous and enlarged inferior pancreaticoduodenal
artery (IPdA; arrow).
Fig. 3 Sagittal maximum-intensity projection (A ) and volume-rendered (B ) computed tomographic images showing severe stenosis of the celiac trunk orifice
(arrow).
Fig. 4 Coronal thick-slab magnetic cholangiopancreatography image (A ) with standard (B ) and zoomed-in (C ) T2-weighted images showing band-like impingement (arrow) of the distal common bile
duct and resultant mild upstream dilation.
Ursodeoxycholic acid was prescribed to relieve the bile passage. No intervention was
considered, given the asymptomatic mild elevation in liver enzyme levels. The patient
has been under hepatic surveillance, with no specific symptoms regarding the hepatobiliary
system at the time of this writing.
Discussion
The hypothesis that pulsatile arterial compression on extrahepatic biliary passage
might be responsible for cholestatic state in some patients was first raised in the
1960s.[3 ] The first two cases were documented in 1984,[1 ] and several other cases have been added to the existing literature since then.[2 ]
[3 ]
[4 ]
[5 ]
[6 ]
[7 ] Presenting symptoms in those cases were mainly jaundice, bile stone formation, and
cholangitis, all of which could be attributed to cholestasis caused by the compression.[1 ]
[2 ]
[3 ]
[4 ]
[5 ]
[6 ]
[7 ] In other words, compression of the EBS leads to bile stasis, which may be further
complicated by infection and/or hepatolithiasis.[8 ]
Compression of the EBS by the right hepatic artery was named as “right hepatic artery
compression syndrome,” since, not surprisingly, the leading actor in those cases was
the right hepatic artery. In a descriptive study, causative arteries were identified
as the right hepatic artery, an unspecified branch of the common hepatic artery, gastroduodenal
and cystic artery, and the proper hepatic artery, in decreasing order of frequency.[9 ] In the same study, the most common site of compression was noted as the common hepatic
duct, followed by the left hepatic duct, proximal CBD, and the right hepatic duct.[9 ] Our case is unique in a way that the causative artery was the IPdA branches, and
the compression site was the distal CBD. In our case, preocclusive stenosis of the
celiac trunk led the way to the formation of enlarged anastomoses between the superior
and the inferior PdAs, which are mainly supplied by the celiac trunk and the superior
mesenteric artery, respectively. When these enlarged anastomoses were further complicated
by severe atherosclerosis, the distal CBD was somehow compressed, which might have
been the underlying cause of the longstanding impaired liver function tests in our
patient.
It is of utmost importance to rule out other pathologies that can be responsible for
the compression of the EBS since vascular compression syndrome is an exclusion diagnosis.[7 ] US, CT, MRCP, and endoscopic retrograde cholangiopancreatography are the imaging
modalities that can be used to accurately assess the presence, level, and cause of
EBS compression.[10 ] In suspicion of vascular compression syndrome, angiographic modalities should follow
the aforementioned modalities.
The importance of this case report lies in the fact that vascular structures neighboring
EBS should be thoroughly assessed, especially in the case of cholestatic state of
unknown etiology. We, herein, propose an umbrella term for all these phenomena: “vascular
compression syndrome.” The aim of this case report is to draw attention to the neighboring
structures regarding EBS, which may shed light on some of the cases with cholestasis
of unknown etiology.
In conclusion, anatomical and/or topographic variations, other than the hepatic artery's,
should also be considered during the evaluation of the EBS compression.
